Try square



June 28, 1949. 'c. E. GANCER 2,474,577

I TRY-SQUARE 7 Filed Feb. 15, 1946 Patented June 28, 1949 UNITED STATES PATENT OFFICE TRY SQUARE Charles E. Gancer, Oak Park, Ill.

Application February 15, 1946, Serial No. 647,833

4 Claims.

The present invention relates to a tool-makers and machinists precision try-square of enhanced and permanent accuracy.

It is one of the objects of the presentinvention to produce a square made up of two pieces which, when properly assembled, will be productive of a try-square of an extremely high degree of precision.

A further object of the invention is to provide a try-square made up of parts, a supply of which may be made separately, with the absolute assurance that when any two of them are properly interfitted they will be productive of a perfect and accurate try-square.

Still a further object of the invention is to produce a try-square having a straight edge which is a portion of a cylindrical surface so that it will lie accurately along the surface which is to be gauged therewith.

Still a further object of the invention is to produce a two part try-square which is easily assembled and disassembled but which nevertheless will retain its absolute accuracy.

Further objects of the invention will become apparent from the further description and claims herein.

The invention is illustrated in a sheet of drawings in which Fig. 1 is a side elevational view of the complete square;

Fig. 2 is a fragmentary side elevation, on a somewhat enlarged scale, of the blade of the square together with the head thereon, the latter being shown partially in section;

Fig. 3 is a top plan view of the blade and its head;

Fig. 4 is an exploded perspective view, partly in section, showing the blade, the head, the stock, the recess in the stock, and the assembly screws;

Fig. 5 is a section along the line 5-5 of Fig. 1, but on a larger scale than said figure, and

Fig. 6 is an end view of the blade on the same scale as Figs. 2, 3 and 5.

The square comprises the base or stock 7, which is rectangular in cross section; the bottom face 8 and the top face 9 of which are accurately machined into two opposed absolutely parallel faces.

If desired, the sides l and Il may also be machined or ground into parallelism.

The blade I2 is provided with a somewhat heavier head l3 and is provided with two exactly parallel opposed straight edges l4 and I5. In order to produce these straight edges the blade, together with its head, is set up on centers by aid of the openings l6 and I1, so that it may be rotated on a longitudinal axis extending from the apices of these respective openings I6 and I1;

while so rotated, the edges l4 and I are ground, thus producing straight edges, having an arcuate surface, which are in effect a portion of the same cylinder of rotation about the axis of the openings Iii-41. The edges are further beveled at it relative to edge l5, and at l9 relative to edge I4. This beveling may be either hollow or straight. It will be seen that the arcuate edge [5 as well as the bevel l8 also extend on to the head I3. The other side of the head, however, is made arcuate but is set back from the edge M as can best be seen from Figs. 2 and 6. The end 2| of the head I3 is machined to a condition of absolute right angularity with the edges M and I5, this best being accomplished by machining followed by grinding. There will thus be produced a blade which is absolutely accurate by reason of the fact that the edges are ground on centers. Moreover the seat 2| at the end of the blade head I3 is also ground at right angles on centers. The blade is therefore perfectly .square with the gauging edges and likewise with any angle within its cylindrical surface. As all three grinding operations on the blade are performed on centers, the three respective surfaces will of course be concentric with said centers and therefore absolute accuracy in the blade is assured by the process of its production.

The base or stock"! which is to have exactly parallel surfaces 8 and 9 is made as follows:

There is first cut into it at one end the recess 22 which is congruent with the end 20 of the head l3 of the blade [2. The bottom of the recess 22 comprises a seating surface 23 which is produced as follows: There is first machined,

at the bottom of the recess and surrounding the surface 23, a clearance groove 24, and also a groove 25. There are also drilled, from the face 8 of the stock, two screw-receiving holes 26 and 21 which terminate at the surface 23 and which are made very slightly larger than the screws 28 and 29 which are used to assemble the square, as will be more fully described hereinbelow. The recess 22 and the grooves 24 and 25 having been formed, and the holes 26 and 27 having been drilled, the surfaces 8 and 9 of the stock I are then machined into absolute parallelism with each other. Thereafter, and using surface 8 as a guide, the surface 23 at the bottom of the recess is machined into accurate parallelism with the surfaces 8 and 9. By reason of the fact that the clearance groove 24 has been provided, this is readily accomplished.

It will be noticed that a small notch 30 has also been provided in the face 9 of the stock at the semi-cylindrical portion of the recess 22, this being for the purpose of. allowing clearance for the slightly protruding bevel l8 and edge M of the blade beyond the curved surface 20 of the head thereof when the square is in assembled relation.

If desired, the surfaces 2| and 23 may be lapped towards the outside of the square and the edge 1 I4 toward the inside of the square, thus placing the rounded portions 20 against the correspondingly curved cylindrical portions ofthe recess 22 with a portion of the edge I4 lying partly within the notch 30. This thus brings the edges 14 and I5 into a direct right angular relationship with the surfaces 8 and 9 of the stock 1. It will be noticed also that the blade edge I5 extends slightly beyond the end of the stock I on the outside of the same, so that it will allow for a slight clearance at the extreme bottom of an inside right angle when the outside of the square is to be used to-test it for accuracy.

Screws 28 and 29, preferably of the so-called Allen type containing a hexagonal recess in their heads, are used for assembly purposes. The threaded portions of the screws, while they accurately engage the openings 3| and 32, are slightly smaller than the internal diameter of the openings 21 and 26, so that there will be no binding'of these screws inthe said holes.

There is also a certain amount of clearance at the extreme ends of the holes 3| and 32, so that the screws 28 and 29 will not completely enter the said holes, the result being that when the screws are drawn up they will accurately align surfaces 2| and 23. As can best be seen from Fig. 5, the holes 26 and 21 are provided with a countersink 33 made deep enough so that the head 34 of the screws 28 and 29 will lie below the outside surface 8 of the stock so that the said screws will not interfere with the accuracy of the instrument. The head .34 of the screws thus abuts against the inner edge 35 of the countersink 33.

When in fully assembled position, the square is absolutely accurate and will retain its accuracy. By reason of the fact that both the stock I as well as the blade 12 may be separately produced, it is possible to thereby produce parts for a number of squares without there being a liability 0f the parts being inaccurate when assembled.

The stockand blade are preferably both made from high grade tool steelwith the surfaces suitably hardened so as to prevent undue distortion and damage thereof in use.

Applicant claims:

1. A precision square comprising a stock having opposed parallel working faces and provided with a recess at one end, the bottom of said recess being accurately ground to a condition of parallelism with said opposed faces; a bevel-edged blade having an enlarged head, the end of said head being accurately ground at a 90 degree angle to the edges of said blade and provided with threaded screw-receiving openings; said stock having screw-passing openings extending from the outer face thereof-andterminating-at the bottom of said recess; said head lying Within said. recess with.

its end in contact with the bottom of said recess; and screws, passing throughthe openings in said stock and engagingthe .threadedopenings in said head, whereby to secure the blade and stock in assembled relation.

2. A precision square comprising a massive rectangular stock and. a thin blade having a thick head; said stock having accurately ground opposed parallel working faces and a recess at one end, the bottom of said recess being ground into exact parallelism with the inner and outer working faces of said stock and provided with a horizontally and vertically extending clearance groove; said stock being provided with holes for the passage of fastening means, which holes originate in the outer working face of the stock and terminate at the ground surface of said bottom; the blade and end of its head being accurately machined to provide beveled edges on the blade, and an end on said head that is at exactly a right angle with said edges, said end being provided with inwardly extending fastening-meansreceiving openings; said head accurately interfitting with said recess with the end of the head in abutting contact with bottom of said recess; and fastening means extending through said holes and into said openings to secure the blade and stock in assembled relation.

3. A' precision square having a rectangular stock provided with parallel opposed ground working faces and with a recess at the inner end of said stock, said recess being bottomed by a smooth contacting seating surface that is precisely parallel with said faces and provided with a surrounding clearance groove; the stock being penetrated by holes originating on the outside of the stock and terminating at said surface; and a thereto fitted blade having a head congruent in size and. shape with said recess and having its abutting end accurately ground to make substantially perfect contact with said surface, the blade being. provided with edges that are exactly at degrees to the said abutting end, said end being provided with threaded screwreceiving holes in register with the holes in the stock; and. countersunk screws passing through the stock and into the abutting end ofthebladehead serving to securethe blade and stock in assembled relation.

4. A precision square comprisinga stock having opposed parallel working faces and provided with a recess at one end, the bottom of said recess being accurately ground to a condition of parallelism with said opposed faces; a bevel-edged blade having an enlarged head, the end of said head being accurately ground at a 90 degree angle to the edges of said blade and provided with a threaded screw-receiving opening; said stock having a screw-passing opening extending from the outer face thereof and. terminating at the bottom of said recess; said head lying within said recess with its end in contact with the bottom of said recess; and a screw, passing through the opening in said stock-and engaging the threaded opening in saidhead, whereby to secure the blade and stockin assembledrelation.

CHARLES E. GANCER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number. Name Date 484,575 Wetterhahn Oct. 18, 1892 2,315,004 Painter Mar. 30', 1943 2,379,048 Thomas June 26, 1945' 

